It is clear that accompanied with recent worldwide increase in population, productivities of important crops will influence food economy in various countries. Accompanied with these changes, a conventional agricultural system will be inevitably changed toward the 21st century. At present, development of a herbicide which can economically and efficiently kill or control weeds which are problems when crops are grown has been demanded more strongly by farm workers as compared with before.
As such a herbicide, development of a chemical which can meet the following requirements has been desired.
There have been desired a chemical having a high herbicidal effect with a small dose (it is necessary to kill weeds by. spraying a dose as small as possible particularly from the standpoint of protection of environment), a chemical having a moderate residual effect (in recent years, there has been a problem that a chemical which remains in soil for a long time causes damage to subsequent crops so that it is important to have a moderate residual effect after spraying), a chemical which can kill weeds rapidly after spraying (after treatment with a chemical, next crops can be planted or transplanted in a short period), a chemical of which the number of treatment times is small (for farm workers, it is important to reduce the number of times of cumbersome weed-controlling operation as far as possible), a chemical having weed-controlling effects on various weeds (a chemical which can control weeds having different properties such as broad-leaved weeds, grass weeds, perennial weeds, etc. by itself is desired), a chemical having many application methods (if a chemical has a soil treatment effect, a stem and foliar treatment effect, etc., a stronger herbicidal effect can be obtained) and a chemical which does not cause problematical chemical damage to crops (it is preferred to kill only weeds selectively in a cultivated field where crops and weeds coexist). However, existing herbicides cannot meet all of these requirements.
Further, in order to regulate growth of a plant by a chemical substance, there have been used conventional commercially available chemicals, for example, daminozide (general name), maleic hydrazide (general name), mefluidide (general name), etc. for the purpose of controlling growth of a plant, controlling a lateral bud, controlling growth of a lawn, etc. However, these compounds have problems that they should be used at high concentrations, their application places and application times are limited, their effects are unstable so that chemical damage is likely caused, etc.